JP 2011-113642 A (hereinafter referred to as “Document 1”) discloses a lighting device including a converter which uses electric power from an input power supply to output electric power required by a load. The lighting device described in Document 1 is configured so as to reduce an output current output from the converter in a range in which an input voltage to the converter is lower than a threshold voltage.
However, in a power supply device configured to simultaneously control a plurality of converters, an input voltage to each of the converters decreases more in the case of operation of the plurality of converters than in the case of operation of one converter. In a range in which the input voltage is lower than a threshold voltage, a reduction amount of an output from each converter increases more in the case of operation of the plurality of converters than in the case of operation of one converter. Thus, in accordance with the operation status of the plurality of converters, the input voltage varies, and an output from each converter thus also varies.